Optical fibers have made a significant impact on sensing technologies due to their intrinsic immunity to electromagnetic interference, electrical passivity, high resolution and large dynamic range. An important new class of optical fiber has recently emerged: microstructured optical fibers (“MOF”), which presents new alternatives for a multitude of scientific and technological applications by means of synergistically integrating optics and microfluidics in a single fiber with unprecedented light path length. However, existing fibers are all based on silica, which is inherently unstable in chemically harsh environments at high temperatures. As the demand for advanced systems increases in areas such as aerospace, sustainable energy, military security, and industrial processes, sensor technologies that can function under extreme operating conditions become of critical importance. Sapphire optical fibers offer an excellent alternative due to their known chemical and thermal stability, but microstructured versions cannot be readily made as in the case of silica MOF. Additionally, commercially available and optical-quality sapphire fibers rated for high temperatures are all free of cladding. Unclad sapphire fiber is extremely sensitive to attenuation due to scattering and absorption by particulate deposits and contaminants within a service environment. Further, the ˜1.77:1.0 index contrast between sapphire fiber and air in the visible range results in rapid decay of the evanescent field from a fiber surface to its surroundings, limiting the field-analyte overlap for sensing interrogation.